1. Field
The present invention is directed to a light pipe having an improved structure of prisms.
2. Background
An illuminating apparatus using a light pipe by which a light can be transmitted to far distance with relatively small transmission loss is known in the art. The light pipe is also called as a light conduit, an optical guide, or a light tube, and is used for effectively distributing a decorative or functional light over a relatively large area.
Below, the principles of light transmission and reflection of the light pipe having the above construction will be explained in the scope necessary to understand the present invention with reference to the drawings.
FIG. 1a is a cross-sectional view illustrating part of an optical lighting film for describing transmission and reflection in a light pipe used in illuminating system in the art. And, FIG. 1b is a perspective view illustrating part of an optical lighting film for describing transmission and reflection in a light pipe used in illuminating system in the art.
Referring to FIG. 1a and FIG. 1b, a light from a light source (not shown) is incident and refracted to an unstructured inner side of the optical lighting film (point 1), total-reflected on both sides of a prism of the structured outer side (point 2 and point 3), whereby the light proceeding to outside is refracted at the inner side (point 4), and is inputted again to inside, as shown by the arrow. As this total-reflection process is repeated, the light is substantially proceeding along with the longitudinal direction of the light pipe. Thus, the transmission ability of a light generated from the light source can be enhanced by using the optical lighting film.
The conventional light pipe like the above improves the transmission ability of a light generated from a light source by using the optical lighting film, but it was difficult to emit the light mote toward a certain direction.